Condition responsive switch device

ABSTRACT

A condition responsive switch device comprising a member with a liquid passageway therein, a reservoir of conductive liquid, such as mercury, at one end of the passageway defining a movable contact, a stationary contact at the opposite end of the passageway normally spaced from the conductive liquid but contacted thereby under predetermined conditions. Preferably, an expansion chamber is provided above the passageway permitting uninhibited movement of the conductive liquid toward the stationary contact. In addition, a solid conductor may be provided in the passageway to reduce the volume of the conductive liquid and increase the current carrying capacity of the device.

United States Patent [1 Scarelli 1 June 11, 1974 [54] gg jgg RESPONSWESWITCH FOREIGN PATENTS OR APPLICATIONS 957,227 9/]927 Australia 337/331[76] Inventor: David F. Scarelli, 214% E. Spruce 1,233,461 2/1967Germany 337/331 St., East Rochester, N.Y. 14445 [22] Filed, Jam 3, 1973Prirnary EXamir IeF-Bernard Gilheany Asszstant Examiner-A. T. Grlmley PP320,814 Attorney, Agent, or Firm-Clarence A. OBrien; Harvey B. Jacobson[52] [1.5. CI 337/331, ZOO/84 R, 2OO/l9l,

337/21, 337/119, 337/122, 337/332 ABSTRACT [51] 111i. Cl. 01h 37/36 Aondition responsive switch device comprising a Fleld of Search member apassageway therein, a reservoir 337/222, 298, 320, 321, 324, 331, ofconductive liquid, such as mercury, at one end of 416; 340/329; 200/84R, 84 A, 84 B, 191, the passageway defining a movable contact, astation- 192, 213; 335/52, 56 ary contact at the opposite end of thepassageway normally spaced from the conductive liquid but contactedReferences Cited thereby under predetermined conditions. Preferably,

UNITED STATES PATENTS an expansion chamber is provided above thepassage- 1,945,434 1/1934 Greer 337 331 x y Permitting uninhibitedmovement of the conduc- |979,441 1 H1934 Benya I I i D I goo/g4 B X tiveliquid toward the stationary contact. In addition, a 1,992,066 2/1955Greer 337/331 X solid conductor may be provided in the passageway to2,709,738 5/1955 Walter 336/52 X reduce the volume of the conductiveliquid and in- 3,028,464 4/1962 ZCHFfO-SS, Jr, 337/33l X crease thecurrent carrying capacity of the device. 3,l42,736 7/1964 Mitchell335/52 3,361,995 1/1968 Marcum 335/56 16 Claims, 8 Drawing FiguresPAIENTEB N Y 1 I97 3.815.816 sum 1 or 2 1 CONDITION RESPONSIVE SWITCHDEVICE The present invention is generally related to switch devices and,more particularly, to an improved, relatively simple switch device forsensing predetermined high temperatures, or pressure conditions.

In the past, various switches have been provided for sensingtemperatures and pressure conditions. Several conventional switchesutilized mercury, or other conductive liquid, which was displaced inresponse to predetermined temperature conditions, or the like, to effectswitching. For the most part, these switch devices were comprised ofextremely delicate components which were subject to easy damage,particularly during shipment. Furthermore, such switches often requiredassembly after they were shipped from the factory, whereby the purchaserwas required to supply mercury and calibrate the switch. This was asource of considerable aggravation and often led to errors. Also, suchconventional switches were either very limited in their current carryingcapacities, making them unsatisfactory for many applications, orrequired a considerable volume of costly mercury which significantlyincreased the price of the device.

It is an object of the present invention to provide an improvedcondition responsive switch device of compact construction including aminimum number of parts and which may be calibrated or preset at thefactory to respond to predetermined conditions in the field.

Another object of the present invention is to provide a noveltemperature responsive device which is of heavy duty construction andwhich is calibrated and sealed at the factory prior to shipment.

A further object of the present invention is to provide a versatiletemperature responsive switch device including a thermally expandableconductive liquid, part of which is displaced through a passageway intoan overflow reservoir to calibrate or preset the device for a desiredresponse temperature.

Still another object of the present invention is to provide a compact,highly reliable temperature responsive switch which is readily adaptablefor use with building structure fire alarm systems, with several of theswitches being placed at various locations throughout the buildingstructure.

It is another object of the present invention to provide a unique switchdevice with both a solid conductor and conductive liquid disposed in acapillary-like passageway to increase the current carrying capacity ofthe switch without significantly increasing the total volume ofconductive liquid required.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout.

FIG. 1 is a perspective view of a first embodiment switch device of thepresent invention together with a schematic diagram of a typical alarmcircuit.

FIG. 2 is a longitudinal sectional view of the device shown in FIG. 1.

FIG. 3 is a cross-sectional view taken along section 3-3 of FIG. 2.

FIG. 4 is a cross-sectional view taken along section 4-4 of FIG. 2.

FIG. 5 is an exploded perspective view of the device shown in FIG. 1.

FIG. 6 is a partial sectional view of the device shown in FIG. 2 withthe conductive liquid flowing into the overflow reservoir duringcalibration.

FIG. 7 is a longitudinal sectional view of a second embodiment of thepresent invention.

FIG. 8 is a cross-sectional view taken along section 88 of FIG. 7.

Referring now, more particularly, to FIG. 1 of the drawings, thecondition responsive switch device of the present invention is generallyindicated by the numeral 10 and includes upper and lower end caps 12 and14, preferably of conductive material and of cylindrical configuration.The end caps are spaced from each other by a center member 16,preferably of glass or other non-conductive material. Center member 16is provided with an elongated liquid passageway which permits the flowof mercury, or other conductive liquid between upper and lower caps 12and 14, under predetermined temperature conditions, as hereinafterexplained.

The switch device is of relatively compact construction and is adaptedto detect high temperatures, such as those normally associated withhazardous fire conditions. Caps 12 and 14 may be appropriately connectedto a conventional alarm circuit, such as that indicated at 17 includinga battery or other voltage source 18 and an audio alarm or otherindicator 20. When the switch device senses a predetermined temperaturecondition, it effects closure of the circuit to energize the alarm. Itwill be appreciated that several of the switch devices may be placed atvarious locations in a building structure and connected in parallel tothe alarm circuit, such that high temperatures sensed by any one of thedevices will effect closure of the circuit. Of course, it is notintended that the device be limited to use with the circuit illustrated,as any appropriate alarm circuit may be utilized dependent upon theparticular application.

Referring now, more particularly, to FIGS. 2-5, the structure of theswitch device of the present invention may be seen in more detail. Itwill be observed that center member or body 16 is of generallycylindrical configuration with upper and lower portions 22 and 24 oflesser diameter than a medial spacer portion 26. The medial portiondefines a pair of circular shoulders 28 and 30 which are abutted by theend surfaces of the upper and lower caps 12 and 14. Lower cap 14 isretentatively mounted to center member 16 and defines in part areservoir which is filled with mercury, or other conductive liquid 32which expands with an increase in temperature. An elongated, relativelynarrow passageway 30 extends between the upper and lower ends of centermember 16. Upon heating, the mercury expands and is forced up intopassageway 30 through a lower opening 34. Preferably, the lower end ofbody 16 is provided with surfaces 36 which slope slightly upwardly andinwardly toward the lower opening. This prevents the entrapment of airor other gases in the reservoir when the conductive liquid is expandedup into passageway 30.

A stationary contact 38 is disposed immediately adjacent the upperopening of passageway 30 and is provided with a relatively smallaperture 40 which is in general alignment with the upper opening of thepassageway. Preferably, the stationary contact is of generally conicalconfiguration with peripheral edge portions which are retentativelyengaged by upper cap member 12. The stationary contact is made ofrelatively thin, deformable material, such as copper, with theperipheral edge portions being bent down by the upper cap member duringassembly. This sandwiches the peripheral edge portion of the stationarycontact between the center member 26 and upper cap 12, as indicated at42.

It will be appreciated that the conductive liquid expands upon heating,such that when it is heated to a predetermined temperature, it is forcedup passageway 30 and makes contact with stationary contact 38. This iseffective to energize an alarm or cause closure of another appropriatecircuit. The temperature at which the conductive liquid comes in contactwith stationary contact 38 is dependent upon the coefficient of thermalexpansion of the conductive'liquid and the volume of conductive liquidwhich must be displaced in order that the conductive liquid reach thestationary contact. Once the reservoir has been sealed, for eachtemperature, there is a corresponding position for the height of theliquid column in passageway 30. This makes it possible to calibrate thedevice for circuit closure at a predetermined temperature. With aconsiderable volume of conductive liquid in the reservoir, sufficientheating will cause the liquid to be displaced through aperture 40 of thestationary contact 38. This is best illustrated in FIG. 6. As the liquidis forced through the aperture, it tends to roll down the inclinedsurfaces of the stationary contact which is conical in shape. Thus, theinclined surfaces in effect define an overflow reservoir. The overflowmercury or other conductive liquid accumulates in the form of globules,such as indicated at 46. When the temprature is subsequently decreased,the column of mercury recedes down passageway 30, leaving globules 46 inthe overflow reservoir. This calibrates the device for switch closure atthe calibration temperature. Thus, when the conductive liquid is againheated to the calibration temperature, the top of the liquid column willjust come in contact with stationary contact 38 to effect circuitclosure. 1

It will be appreciated that aperture 40 is of relatively smalldimension, preferably 5 mils in diameter. Since the surfaces of thestationary contact slope away from aperture 40, once the switch has beencalibrated, it is impossible for the conductive liquid to return topassageway 30 under the influence of gravity or even mild shaking of thedevice. This is due in part to the surface tension of each globule ofmercury which prevents the globule from breaking up to fit through theaperture.

Upper cap 12 defines an expansion chamber 48 which is filled with air orother gas. This allows the device to be sealed from the atmosphere, butat the same time permits the conductive liquid to move up through thepassageway substantially unhindered by any pressure. The gas within theexpansion chamber, however,

is slightly compressed during high temperature conditions and appliesmild pressure against the liquid column which aids in returning theconductive liquid down through the passageway upon cool down aftercalibration. Preferably, a pressure of approximately 1.5 atm. at roomtemperature is provided within the expansion chamber. This is achievedduring assembly as the upper cap is forced over the upper portion ofcenter member 16 until it abuts shoulder 28. It will be appreciated thatby providing the expansion chamber in the upper cap, the switch devicewill not explode when exposed to high temperatures, as is the case withmany conventional fire detecting devices.

Referring now, to FIGS. 7 and 8, a second embodiment of the presentinvention is generally indicated by the numeral 50 and is similar to thefirst embodiment, but is provided with a liquid passageway 52 of largerdiameter or cross-sectional area. This increases the current carryingcapacity of the device, such that it may be utilized with alarm circuitsdrawing considerably more current than those which would be utilizedwith the first embodiment. Since the cross-sectional area of the liquidpassageway is greater, the resistance to electrical current flow issignificantly decreased. However, it has been found thatsuch an increasein cross section requires a considerable increase in the volume ofmercury or other conductive liquid being utilized. This is undesirable,since the cost of mercury is considerably high. In addition, there aremany solid metals of better electrical conductivity than mercury. Inorder to increase the current carrying capacity without significantlyincreasing the cost of the device, an elongated, solid conductor 54,preferably of copper, is inserted into the device during assembly. Thesolid conductor extends at least partially into passageway 52 and is ofa diameter or transverse dimension less than that of the passageway,such that it is substantially surrounded by a layer of mercury and isfree to move within the confines of the passageway. When circuit closureis effected, current is caused to flow through both the conductiveliquid and the solid conductor. Since the cross-sectional area isgreater and the resistivity of the copper conductor is significantlyless than mercury, the second embodiment provides much greater currentcarrying capacity. Preferably, the solid conductor is of a lesserspecific gravity than the conductive liquid, such that it tends to floatin the liquid and move up the passageway as the temperature isincreased. It will be appreciated that this provides a unique means ofincreasing the current carrying capacity of the switch device, withoutincreasing the total volume of mercury required. In some cases thevolume of mercury may be less than that of the first embodiment,depending upon the relative dimensions of the solid conductor and thepassageway.

From the foregoing descriptions, it will be appreciated that thecondition responsive switch device of the present invention provides acompact, relatively simple, yet highly versatile means of sensingpredetermined temperature conditions. The manner in which the upper endof the center member is contoured pro vides an overflow reservoir foreasy calibration of the device. By merely heating the device to thedesired temperature, it is automatically calibrated. The switches may beaccuratelycalibrated in large numbers by merely placing in a temperaturecontrolled oven, or otherwise exposing them to the desired temperature.Preferably, the device is only 1.025 inches in length and 0.375 inch indiameter, providing an extremely compact structure which may be mountedin almost any location in a building for connection to a fire detectionalarm system. Of course, it is not intended that the invention belimited to the embodiments illustrated. The center member need not bemade of glass or other insulating material, so long as it is insulatedfrom the stationary contact and upper cap. Furthermore, the upper andlower caps need not necessarily be conductive, as other appropriatemeans of completing the circuit through the liquid reservoir andstationary contact may be provided. Also, the stationary contact neednot be conical in configuration, so long as it is disposed adjacent theupper opening of the liquid passageway, and the upper end of the centermember is of appropriate configuration to define an overflow reservoirfor calibration purposes. It should also be noted that the presentinvention is not limited to use solely as a tempera- .ture responsivedevice. It is possible to connect the mercury reservoir in communicationwith conventional pressure bellows, diaphragms or the like to effectdisplacement of the mercury in response to predetermined pressureconditions.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. A temperature responsive switch device, said device comprising acenter member of non-conductive material with an upper end and a lowerend, a fluid passageway extending through said center member betweensaid upper and lower ends and terminating at upper and lower openings,respectively, a reservoir of conductive liquid beneath saidnon-conductive member and expandable into said fluid passageway throughsaid lower opening under predetermined temperature conditions, a lowerconductive terminal electrically connected to said reservoir ofconductive liquid, a stationary contact adjacent said upper opening andnormally spaced from said conductive liquid, said stationary contactbeing contacted by said conductive liquid when the liquid is at atemperature greater than a predetermined limit, and overflow reservoirmeans surrounding said upper opening for draining said liquid away fromsaid upper opening when said liquid is passed through said upperopening, whereby said device may be calibrated to complete a circuit atsaid predetermined temperature limit, said reservoir means being definedby surfaces adjacent said upper opening and sloping downwardlytherefrom, said stationary contact being generally conical inconfiguration and overlies said upper end of said center member todefine said sloped surfaces, said conical stationary contact includingan aperture therein in general alignment with said upper opening toallow the passage of liquid therethrough.

2. The device set forth in claim 1 together with an upper conductive capmounted to said center member at its upper end and retentativelyengaging the peripheral edge portions of said conical stationary contactto hold it in place.

3. The device set forth in claim 2 wherein said upper conductive capdefines. a sealed expansion chamber overlying said upper opening topermit the uninhibited flow of said liquid through said passageway.

4. A condition responsive switch device. comprising a non-conductivebody having a fluid passageway extending therethrough between oppositelongitudinal ends, conductive reservoir means extending from one of theends of the body for enclosing a conductive fluid expansible into thefluid passageway, a conductive housing non-conductively spaced from thereservoir means enclosing a fluid overflow space adjacent the other endof the non-conductive body, contact means mounted directly on said otherend of the body in en gagement with the conductive housing for contactby the conductive fluid in the fluid passageway and oneway passage meansin the contact means for conducting fluid in one direction only from thepassageway to the overflow space, to enable calibration of the switchdevice.

5. The combination of claim 4 wherein said body includes an intermediatespacer portion nonconductively spacing the reservoir means and thehousing from each other.

6. The combination of claim 4 wherein said contact means comprises aconical element having an apex at which said one-way passage means islocated.

7. The combination of claim 6 wherein said body includes an intermediatespacer portion nonconductively spacing the reservoir means and thehousing from each other.

8. A condition responsive switch device comprising a center member withupper and lower ends, a passageway extending through said center memberbetween upper and lower openings at said upper and lower endsrespectively, a stationary contact adjacent said upper opening, areservoir of conductive liquid at the lower end of said center member,said conductive liquid defining a movable contact which is displaceablethrough said passageway for contact with said stationary contact underpredetermined conditions, and solid conductor means in said conductiveliquid and extending longitudinally into said passageway along asubstantial length thereof to provide a relatively low electricalresistance path through said passageway.

9. The combination of claim 10 including a lower conductive terminalelectrically connected to said reservoir of conductive liquid, andoverflow reservoir means surrounding said upper opening for drainingsaid liquid away from said upper opening when said liquid is passedthrough said upper opening. I

10. The device set forth in claim 9 wherein said solid conductor meansis of a specific gravity less than that of said conductive liquid, suchthat said solid conductor means floats in said conductive liquid.

11. The structure set forth in claim 8 wherein said solid conductormeans is movable relative to said passageway.

12. The structure set forth in claim 11 wherein said solid conductormeans is of a specific gravity less than that of said conductive liquid.

13. The structure set forth in claim 8 wherein said device includes alower cap mounted to the lower end of said center member which togetherwith said lower end defines said reservoir.

14. The structure set forth in claim 13 wherein said device includes anupper cap mounted to the upper end of said center member and in sealingengagement therewith, said upper cap together with the upper end of saidcenter member defining chamber means for permitting the uninhibitedmovement of said conductive liquid up said passageway.

15. The structure set forth in claim 14 wherein said solid conductormeans is movable relative to said passageway.

16. The structure set forth in claim 15 wherein said solid conductormeans is of a specific gravity less than that of said conductive liquid.

1. A temperature responsive switch device, said device comprising acenter member of non-conductive material with an upper end and a lowerend, a fluid passageway extending through said center member betweensaid upper and lower ends and terminating at upper and lower openings,respectively, a reservoir of conductive liquid beneath saidnon-conductive member and expandable into said fluid passageway throughsaid lower opening under predetermined temperature conditions, a lowerconductive terminal electrically connected to said reservoir ofconductive liquid, a stationary contact adjacent said upper opening andnormally spaced from said conductive liquid, said stationary contactbeing contacted by said conductive liquid when the liquid is at atemperature greater than a predetermined limit, and overflow reservoirmeans surrounding said upper opening for draining said liquid away fromsaid upper opening when said liquid is passed through said upperopening, whereby said device may be calibrated to complete a circuit atsaid predetermined temperature limit, said reservoir means being definedby surfaces adjacent said upper opening and sloping downwardlytherefrom, said stationary contact being generally conical inconfiguration and overlies said upper end of said center member todefine said sloped surfaces, said conical stationary contact includingan aperture therein in general alignment with said upper opening toallow the passage of liquid therethrough.
 2. The device set forth inclaim 1 together with an upper conductive cap mounted to said centermember at its upper end and retentatively engaging the peripheral edgeportions of said conical stationary contact to hold it in place.
 3. Thedevice set forth in claim 2 wherein said upper conductive cap defines asealed expansion chamber overlying said upper opening to permit theuninhibited flow of said liquid through said passageway.
 4. A conditionresponsive switch device, comprising a non-conductive body having afluid passageway extending therethrough between opposite longitudinalends, conductive reservoir means extending from one of the ends of thebody for enclosing a conductive fluid expansible into the fluidpassageway, a conductive housing non-conductively spaced from thereservoir means enclosing a fluid overflow space adjacent the other endof the non-conductive body, contact means mounted directly on said otherend of the body in engagement with the conductive housing for contact bythe conductive fluid in the fluid passageway and one-way passage meansin the contact means for conducting fluid in one direction only from thepassageway to the overflow space, to enable calibration of the switchdevice.
 5. The combination of claim 4 wherein said body includes anintermediate spacer portion non-conductively spacing the reservoir meansand the housing from each other.
 6. The combination of claim 4 whereinsaid contact means comprises a conical element having an apex at whichsaid one-way passage means is located.
 7. The combination of claim 6wherein said body includes an intermediate spacer portionnon-conductively spacing the reservoir means and the housing from eachother.
 8. A condition responsive switch device comprising a centermember with upper and lower ends, a passageway extending through saidcenter member between upper and lower openings at said upper and lowerends respectively, a stationary contact adjacent said upper opening, areservoir of conductive liquid at the lower end of said center member,said conductive liquid defining a movable contact which is displaceablethrough saiD passageway for contact with said stationary contact underpredetermined conditions, and solid conductor means in said conductiveliquid and extending longitudinally into said passageway along asubstantial length thereof to provide a relatively low electricalresistance path through said passageway.
 9. The combination of claim 10including a lower conductive terminal electrically connected to saidreservoir of conductive liquid, and overflow reservoir means surroundingsaid upper opening for draining said liquid away from said upper openingwhen said liquid is passed through said upper opening.
 10. The deviceset forth in claim 9 wherein said solid conductor means is of a specificgravity less than that of said conductive liquid, such that said solidconductor means floats in said conductive liquid.
 11. The structure setforth in claim 8 wherein said solid conductor means is movable relativeto said passageway.
 12. The structure set forth in claim 11 wherein saidsolid conductor means is of a specific gravity less than that of saidconductive liquid.
 13. The structure set forth in claim 8 wherein saiddevice includes a lower cap mounted to the lower end of said centermember which together with said lower end defines said reservoir. 14.The structure set forth in claim 13 wherein said device includes anupper cap mounted to the upper end of said center member and in sealingengagement therewith, said upper cap together with the upper end of saidcenter member defining chamber means for permitting the uninhibitedmovement of said conductive liquid up said passageway.
 15. The structureset forth in claim 14 wherein said solid conductor means is movablerelative to said passageway.
 16. The structure set forth in claim 15wherein said solid conductor means is of a specific gravity less thanthat of said conductive liquid.